Context manager that wraps another context manager

wrapping_context.py

from __future__ import print_function
from contextlib import contextmanager


@contextmanager
def some_context_manager(x):
    print("Entering", x)
    yield
    print("Exiting", x)


class WrappingContext(object):

    def __init__(self, other_cm):
        self._other_cm = other_cm
        self._current_context = None

    def do_setup_stuff(self):
        print("Setting Up Wrapper")

    def do_teardown_stuff(self):
        print("Tearing Down Wrapper")

    @contextmanager
    def _make_context(self):
        self.do_setup_stuff()
        try:
            with self._other_cm:
                yield
        finally:
            self.do_teardown_stuff()

    def __enter__(self):
        self._current_context = self._make_context()
        self._current_context.__enter__()
        return self

    def __exit__(self, *exc_info):
        assert self._current_context is not None, "Exited too many times!"
        return self._current_context.__exit__(*exc_info)


other_cm = some_context_manager('foo')
with WrappingContext(other_cm) as cm:
    print("In the with block")

# Prints:
#   Setting Up Wrapper
#   Entering foo
#   In the with block
#   Exiting foo
#   Tearing Down Wrapper